Frank,
I dont want to be seen to be a nay-sayer but it is not a combination that I would personally go for.
Technically and by UK regulations you can pull either 100% of the kerb weight or the manufacturers' stated tow limit whichever is the lower. But if you go by the guidelines of the main towing body, the Caravan Club, the accepted safe figure is 85% which puts the figure at 1204 kg for your DS, below the all up weight you quote for your caravan.
We have towed since 1989 the same caravan, an 1989 ABI Marauder 400D, This has an all up weight of 850 Kg and my tow cars have had power outputs of 90 - 132 bhp. My personaldefinition of a successful combo is one that can maintain 60 mph (100 kph) on the flat without undue gear changing and cope with hills with a modest hinderance of other road users. My Montego had around 90 bhp, and was a struggle, my Triumph GT6, just over a 100 was a eye catching tug but boarderline. The initial tow car, a Peugeot 309 SRi (1000kg) was very successful with its petrol 115 bhp, our Xsara (1216Kg) likewise with a HDi 110bhp (still owned) and our Xantia exclusive (132) barely noticed it there !! The point I am illustrating is that 110 was effective pulling its own 1000-1200 kg plus the 850 kg.of our van, the outfit you have suggested has this power to move another 600 Kg which will be a big ask.
A folding caravan is a heavy unit for its size, perhaps the maths of keeping the car and changing the caravan may work out better in the longer run, as having a bigger car for the few weeks of towing annually may be to your financial detriment.
Hope this shines a little more light on a often faced conundrum
D Sport 160